[zifpanachr23]

While new processes don't often get created for mainframes (most of the tasks it is particulary suited for have already been automated by this point, and the market of companies doing those tasks is pretty statics) outside of bolting on more modern interfaces to existing backend, one thing that is often ignored in answering the "why mainframes" question is that the overall amount of compute being done on the platform continues to increase. The same old batch and transaction processing programs get fitted with shiny web frontends and more and more business gets sent to those same old programs. So you can end up in a situation where mainframes remain a very stable business that is worth investing in for future upgrades, even while they become more and more "niche" in the eyes of most computer users over time as the number of computers increases at a faster rate than mainframe capacity increase, so the ratio of computer capacity to mainframe capacity is going up, therefore mainframe capacity is growing substantially while also making up less percent of a larger market over time. Then of course there are the margins, which are much higher than they are for x86_64 servers or other common architecture. A slow and steady increase in demand, mixed with outstanding margins, makes for a good business plan.

Many of the big existing mainframe customers already have multiple max capacity models and are pushing them to their limits as web and analytics and AI/ML and a bunch of other factors increase the overall amount of workload finding their way to mainframes. IBM wouldn't be making those brand new generations of 4-frame models with a new larger max capacity if there weren't customers buying them.